IL180294A

IL180294A - Device for measuring the anglular position of a fin of a projectile

Info

Publication number: IL180294A
Application number: IL180294A
Authority: IL
Original assignee: Nexter Munitions; Giat Ind Sa
Priority date: 2005-12-26
Filing date: 2006-12-25
Publication date: 2012-10-31
Also published as: IL180294A0; EP1801534A1; ATE460638T1; FR2895496A1; FR2895496B1; ES2342316T3; EP1801534B1; DE602006012787D1

Abstract

The measuring device for the angular position of a fin or rudder on a projectile that pivots relative to a fixed support (3) comprises a rotor (13) attached to the fin or rudder axle (4), and a wound stator (16) fixed to the support. The stator, which is set in a recess and fixed to the support by an overmoulded material (18) such as a polymerised resin, has at least two windings - induction and induced - and the rotor co-operates with the stator to form a rotary transformer.

Description

Device for enabling angular position of a projectile fin Giat Industries C. 172169 The technical scope of the invention is that of devices enabling the angular position of a projectile fin or elevon to be measured.

It is known to measure the angular position of an organ, and namely a fin or elevon, by using an electronic angular sensor .

Known sensors are single-piece components comprising a body with a rotating pin. It suffices to link the sensor axis to the fin or elevon axis to measure the displacements of said pin. More often than not, such a link is made by accessory organs, such as intermediate pinions.

A classical sensor is a sensor of the rotating transformer type which comprises a rotor made of soft foliated iron mounted able to pivot with respect to a stator comprising at least two windings, an inductor winding and an induced winding.

However, such a solution has drawbacks when implemented in a projectile and more particularly in a cannon-fired proj ectile .

Indeed, intermediate elements such as the pinions have functional play which leads to errors in the angular positioning measurement of the fin or elevon.

Moreover, the sensors are complicated to assemble.

Assembly requires the positioning of intermediate parts and requires a certain volume. Such an assembly, furthermore, has difficulty withstanding the firing acceleration of the proj ectile .

The aim of the invention is to propose a device to measure the angular position of a fin or elevon which does not suffer from such drawbacks.

The device according to the invention is thus easy to assemble, occupies a reduced amount of space and ensures the measurement of the angular position of the fin or elevon with a minimal amount of error.

The device according to the invention is additionally extremely robust and can withstand being fired from a cannon without being damaged.

Thus, the invention relates to a device to measure the angular position of a projectile fin or elevon which is mounted able to pivot with respect to a support integral with the projectile body, device wherein it incorporates a rotor integral with an axis of the fin or elevon and a coiled stator fixed to the support and incorporating at least two windings, an inductor winding and an induced winding, the rotor cooperating with the stator in order to constitute a rotating' transformer.

The stator will be positioned at the bottom of a bore hole made in the support and intended to receive the axis of the fin or. elevon.

Advantageously, the stator will be made integral with the support by an injection moulding material.

The support may incorporate at least two openings enabling the bore receiving the stator to be linked to the outside.

The invention also relates to an assembly process for such a device.

According to this process, assembly is made easier and ensures the device's robustness during firing.

Furthermore, the relative angular positioning of the rotor and stator is also perfectly controlled.

The process according to the invention is characterised in that it incorporates the following steps: - the stator is placed on tooling which incorporates a first cylindrical seat cooperating with the bore in the stator and a second cylindrical seat of the same diameter as a bore in the support intended to receive the stator, - the tooling carrying the stator is introduced into the bore in the support, · - an injection moulding material is injected between the stator and the support through at least one opening linking said bore to the outside.

The tooling may be made of polytetrafluorethylene, in which case the support will be heated after the tooling has been set into position in order to dilate said tooling.

The support will be cooled after the injection and drying of the moulding material so as to contract the tooling to facilitate its extraction.

The tooling will incorporate a radial hole enabling the positioning of a rod through a slot in the support, the rod ensuring the axial positioning of the tooling and stator.

Additionally, the rotor will be fastened to the fin or elevon axis then this will be positioned in the support and the angular value given by the measurement device will be measured for one position of the fin or elevon corresponding to a nil angle .

Thereafter, the measured angular deviation may be corrected by pivoting the rotor by an inverse angle to the value thus measured, after which the rotor will be permanently immobilised with respect to the fin or elevon axis by integration means.

The invention will be more apparent from the following description of a particular embodiment, such description being made with reference to the appended drawings, in which: - Figure 1 is a schematic view of one part of a projectile equipped with elevons, - Figure 2 is a view of the elevon axis, - Figures 3a and 3b are two partial views of the elevon support, Figure 3a being a section made along the plane whose trace AA is marked in Figure 3b, - Figure 4 shows a first step in the assembly process according to the invention, - Figure 5 shows a second step in the assembly process according to the invention, - Figure 6 is a front view of the rotor alone, - Figure 7 shows the assembled device.

Figure 1 schematically shows a projectile 1 with four fins 2 which here are deployable canard elevons.

These elevons are integral with a support 3 enclosing steering means or a servomechanism to drive them in rotation in order to steer the projectile. These means are not shown in detail and may incorporate two or four back-geared motors (one per canard or one per steering plane) .

The projectile 1 is, for example, a projectile fired by a cannon at a target.

When the projectile is inside the barrel of a weapon (not shown) the canards are' folded along the projectile body 1 or else housed in the projectile body. They deploy upon exiting the barrel to ensure their stabilisation and steering functions .

The deployment mechanisms for the fins or elevons and the drive means for the canard elevons are well known to the Expert and do not form part of the present invention. Reference may be made to patents FR2846079, FR2846080 and FR2864613 as well as patent application FR05-10164 which describe such mechanisms.

Each elevon 2 is integral with an axis 4 mounted able to pivot with respect to the support 3.

Figure 2 focuses in particular on an axis 4. This is globally cylindrical and incorporates a notch 5 delimiting two branches 4a and 4b forming a fork onto which the elevon 2 is mounted and hinged.

The axis 4 incorporates an internal thread 6 at its rear part which is intended to receive a rod (not shown) connected by a ball pivot to a manoeuvring arm (not shown) linking the axis 4 to the elevon' s motorisation.

The manoeuvring arm enables the axis 4 to be made to pivot around its geometrical axis 7.

Figure 3a shows the support 3 alone and section at a bore 8 which is intended to receive the axis 4 of the elevon 2. This bore thus has the same geometric axis 7 and same diameter as axis 4 of the elevon.

A slot 9 is intended to allow a passage for the manoeuvring rod of the axis 4. This slot is surrounded by an oblong counter-sink 10. The support 3 further incorporates openings 19a, 19b, 19c which enables the bore 8 to be linked to the outside. The function of these openings will be described later.

As may be seen in Figure 2, the axis 4 incorporates a cylindrical extension 11 onto which a rotor 13 of a rotating transformer is fastened. The rotor may be more particularly seen in Figure 6. It is constituted by a stack of layers of soft iron (parallel to the plane in Figure 2) bonded to one another and has two symmetrical notches 14a and 14b around its periphery.

The rotor 13 presses against a shoulder 12 of the axis 5 and is made integral with the axis by suitable means, for example, by an assembly 15 associating a screw and a washer, the screw being engaged in an internal thread in the end of the extension 11. The assembly will preferably be completed by a spot of adhesive (bonding will be made after adjustment as will be described hereafter) .

Moreover, Figure 3a shows that the bore 8 encloses a coiled stator 16 with a bore 17 intended to receive the rotor 13.

The stator is shown here schematically. This component also incorporates a foliated soft iron frame around which at least two windings are positioned, an inductor winding and one (or two) induced winding (s).

The windings are not shown in the Figures but such a component is well known to the Expert in the field of rotating transformers.

The rotor 13 associated with the stator 16 constitutes a rotating transformer enabling an angle to be measured.

In accordance with the technology of these transformers (or inductive potentiometers) , when a sine-wave voltage is applied to the inductor winding, a sine-wave voltage is recovered on the induced winding whose amplitude varies linearly as a function of the pivoting angle of the rotor. 1 With a rotor geometry such as shown in Figure 6, angular pivoting of between +90° and -90° may be measured, which is quite sufficient since pivoting of canard elevons is generally of between -10° and +10°.

According to one characteristic of the invention, the rotor and stator are integrated in the measurement device independently of one another and without any specific casing.

According to another characteristic of the invention, the stator 16 is thus made integral with the support 3 by injection moulding 18 which completely encloses the stator 16.

The injection moulding is made of a polymerizable resin. Such an arrangement ensures both the joining of the stator and support, resistance to impact and to acceleration, and this very compactly.

Thus, thanks to the invention, the measurement device is positioned closely to the elevon 2 and measures its pivoting angles, without any measurement transfer play, thus with minimal error.

Furthermore, the device is robust. Its mobile part is integral -with the elevon and its fixed part is mounted with no play using a shock-absorbing material.

The assembly process for such a device will now be described with reference to Figures 4 and 5.

During a first step which is schematised by Figure 4, the stator 16 is placed on tooling 21 which incorporates a first cylindrical seat 22 cooperating with the bore in the stator 16. This seat 22 is delimited by a shoulder 26.

The tooling 21 additionally incorporates a second cylindrical seat 23 of the same diameter as the bore 8 in the support 3 intended to receive the stator 16.

The tooling 21 also incorporates a radial internally threaded hole 24 intended to receive a rod 25 (Figure 5) after the tooling has been put in place in the support 3.

Thereafter (second step) the tooling 21 carrying the stator 16 is introduced into the bore 8 in the support 3 (Figure 5) . During this operation, the wires 28 are made to pass through the opening 19c in the support 3.

To ensure the proper assembly of the stator 16 it is necessary for it to be positioned correctly in its bore 8, both axially and angularly.

In accordance with the invention, the axial positioning is ensured thanks to the rod 25 which is fastened to the tooling 21 through the slot 9 in the support 3.

Somebody skilled in the art will define the tooling 21 such that when the rod 25 is thus positioned, the stator 16 is also axially arranged in the desired place.

The angular position of the stator is roughly ensured by the positioning of the wire 28 in the opening 19c.

Once the stator 16 is in position, the moulding material is injected between the stator 16 and the support 3 through the opening 19b. Openings 19a and 19c enable the air to be evacuated and the filling to be kept under surveillance.

The opening 19b is axially offset with respect to openings 19a and 19c. Such an arrangement enables the housing in the stator to be fully filled in by the resin before it starts to come out of openings 19a and 19c.

Before proceeding with the injection operation, sealing is provided between the tooling 21 and the stator 16.

The tooling may be made, for example, of polytetrafluorethylene, in which case the support 3 is heated after the tooling 21 has been installed so as to dilate it. The temperature merely needs to be raised to 60 °C to ensure the required sealing (as well as the immobilising of the tooling 21 in its bore 8).

To complete sealing, the slot 9 can be sealed off with a filler paste (modelling paste, for example) .

After the injection and drying or polymerization of the resin 18 the support 3 is cooled so as to ensure the contraction of the tooling 21 thereby enabling its extraction.

Additionally, the rotor 13 is fastened to the axis 4 of the fin or elevon 2.

The axis 4 is then positioned in the support 3 (thus, the rotor 13 is positioned in the stator 16) and the angular value given by the measurement device is measured for one position of the fin or elevon corresponding to a nil angle.

The assembly of the rotor in the stator is shown in Figure 7.

The measurement is made using a measurement bench adapted to the rotating transformer constituted by the rotor associated with the stator.

This measurement enables the actual angular offset linked to the assembly to be known.

This offset may then be corrected in two different ways.

Using specific tooling, it is thus possible to make the rotor 13 pivots with respect to the axis 4 by an inverse angle to that previously measured.

After this angular correction, the rotor 13 will be immobilised with respect to the axis 4 of the fin or elevon by joining means, for example a spot of adhesive applied to the end 11 carrying the screw 15.

More simply, the desired angular correction may be programmed in the control electronics for the values which will be measured by the device.

To be on the safe side, this correction using software means will in any event be made systematically to the final integration of the projectile to correct any residual errors with respect to the measurement devices (even if a less refined mechanical correction has already been performed) .

The invention has been described with reference to the measurement of the angular displacement of canard elevons. it is naturally possible for it to be implemented for the measurement of the angular displacements of other types of fins .

Claims

1. A device to measure the angular position of a projectile fin or elevon (2) which is mounted able to pivot with respect to a support (3) integral with the projectile body, device wherein it incorporates a rotor (13) integral with an axis (4) of the fin or elevon (2) and a coiled stator (16) fixed to the support (3) and incorporating at least two windings, an inductor winding and an induced winding, the rotor (13) cooperating with the stator (16) in order to constitute a rotating transformer.

2. A measurement device according to Claim 1, wherein the stator (16) is positioned at the bottom of a bore hole (8) made in the. support (3) and intended to receive the axis (4) of the fin or elevon (2) .

3. A measurement device according to Claim 2, wherein the stator (16) is made integral with the support (3) by an injection moulding material (18).

4. A measurement device according to Claim 3, wherein the support (3) incorporates at least two openings (19a, 19b, 19c) enabling the bore (8) receiving the stator (16) to be linked to the outside.

5. An assembly process for such a device, wherein it incorporates the following steps: the stator (16) is placed on tooling (21) which incorporates a first cylindrical seat (22) cooperating with the bore in the stator (16) and a second cylindrical seat (23) of the same diameter as a bore (8) in the support (3) intended to receive the stator (16), - the tooling (21) carrying the stator (16) is introduced into the bore (8) in the support (3), - an injection moulding material (18) is injected between the stator (16) and the support (3) through at least one opening (19b) linking said bore (8) to the outside.

6. An assembly process according to Claim 5, wherein the tooling (21) is made of polytetrafluorethylene , and wherein the support (3) is heated after the tooling (21) has been set into position in order to dilate said tooling.

7. An assembly process according to Claim 6, wherein the support (3) is cooled after the injection and drying of the moulding material (18) so as to contract the tooling (21) to facilitate its extraction.

8. An assembly process according to one of Claims 5 to 7, wherein the tooling (21) incorporates a radial hole (24) enabling the positioning of a rod (25) through a slot (9) in the support (3) , the rod (25) ensuring the axial positioning of the tooling (21) and stator (16) .

9. An assembly process according to one of Claims 5 to 8, wherein the rotor (13) is fastened to the fin or elevon axis (4) then- this is positioned in the support (3) and the angular value given by the measurement device will be measured for one position of the fin or elevon (2) corresponding to a nil angle.

10. An assembly process according to Claim 9, wherein the measured angular deviation is corrected by pivoting the rotor (13) by an inverse angle to the value thus measured, after which the rotor (13) is permanently immobilised with respect to the fin or elevon (2) axis (4) by integration means (15). For the Applicants REINHOLD COHN AMD PAR1NB5 By: M1 rati